Abstract

Leptin is an important regulator of energy metabolism and reproduction and is mainly synthesized in the adipocytes and then secreted into bloodstream. Leptin receptor is one of regulating components of organism energetic homeostasis. Receptor influences on leptin effects by regulating feed intake, body weight and fat deposition. Leptin receptor gene (LEPR) is located in the sixth chromosome in the region that correlates with content of intramuscular fat, thickness of back fat, growth rate and pig carcass parameters. Due to these correlations, LEPR is known to be gene candidate that controls quantitative traits.

Leptin receptor gene consists of 20 exons; not less than 25 single nucleotide polymorphisms (SNPs) were found in gene structure in different gene sites (exons, introns, 5’ and 3’ regions).

SNPs of LEPR gene can be chosen as useful markers for predicting breeding value in pigs. For the experiment SNP c.232T>A was chosen; it is located in the second exon of LEPR gene.

The aim of work was to study spreading of SNP c.232Т>А in LEPR gene of breeds under Ukrainian selection; to estimate if marker selection for proving meat quality is possible using chosen SNP as a marker.

Materials and methods. For genetic population analysis, DNA samples of Large White breed (bred in Stepne farm, Poltava region, Ukraine) and Mirgorod breed (bred in Dekabristy farm, Poltava region, Ukraine) were used; 50 samples of each breed were taken for the research. Samples were genotyped using PCR-RFLP method. Deviations from genetic equilibrium found using the Hardy-Weinberg coefficient were signified with chi-square criterium, the frequency of alleles, estimation of gene frequencies, determination of heterozygosity were counted using GenAlex 6.0.

Results. Genetic researches showed polymorphism c. 232Т>А in LEPR gene to be spread in population of Large White breed and Mirgorod breed under Ukrainian selection. Polymorphism with AA genotype was shown to be spread the most. In studied Large White population highly probable deviation of the actual distribution of genotypes of the expected value for the Hardy-Weinberg equilibrium (χ2 = 15.759, p ≤ 0.001) was found. The deviation was caused by increasing homozygotes (АА = 0.680). Small amount of heterozygotes (АТ = 0.160) and alternative homozygotes (ТТ = 0.160) was found. Positive designation of Rayt index (0.561) and the advantage of expected heterozygosis (0.365) on the actual (0.160) also show existence of selection pressure of LEPR in this herd. In Myrgorod pig population big amount of animals turned out to be homozygotes АА (0,720), small amount of heterozygotes was found (АТ=0.280), alternative homozygotes TT were not found.

Deviation from spreading of genotypes of the expected value for the Hardy-Weinberg equilibrium was not significant and did not have a significant nature (χ2 = 1.325); SNP variety (c. 232Т>А) in LEPR gene is not spread, so this SNP in Mirgorod breed wasn’t under selection pressure. The fact of low selection pressure of (c. 232Т>А) in LEPR gene in Mіrgord breed can also be proved of negative designation of Rayt index (-0,163) and domination of heterozygotes (0.280). Allele A is found to be dominative above allele T in both studied populations.

Conclusions. After DNA analysis of two breeds under Ukrainian selection (Mirgorod and Large White breeds) polymorphism c. 232Т>А in LEPR gene SNP was found to be spread; chosen SNP can be used for further researches in association analysis for finding correlation between SNP and meat traits.